The present invention relates generally to water supply systems, and more particularly to a system adapted for supplying purified water to one or more water using devices, some of which having distinctive water consumption demands, including devices having distinctively and usually intermittently high demands versus devices having low demands for flow rates and/or volumes of purified water. This invention further presents particular advantages in medical and like high quality purified water supply systems such as in allowing for the supply of water to both high demand dialyzer reprocessing machines and lower demand dialysis machines without substantially increasing the total operational volume or flow rate of purified water flowing through the entire water supply system.
There are presently a variety of industrial and medical devices and associated procedures that require the use of purified water. A prominent example is found in medical dialysis. In such dialysis procedures generally, including hemodialysis, hemofiltration and hemodiafiltration processes, blood to be dialyzed is taken from a patient and passed through a dialyzer where the blood is cleaned of its impurities and then returned to the patient. Contemporary dialyzers are ordinarily of a membrane type in which the blood may be passed along one side of the membrane, while in the most common types of dialysis, another liquid, often called dialysate, may be passed along the opposite side of the membrane. This process is conceptually the same in plate, hollow fiber and coil dialyzers. Ideally, impurities in the blood pass from the blood through the membrane and into the liquid dialysate. The liquid dialysate carrying these impurities then flows out of the dialyzer and is usually passed through a dialysis control monitor or machine to a drain. Some types of dialysis also include providing a replacement liquid to the patient, the replacement liquid being passable with the blood through the dialyzer, or otherwise often being infused directly into the blood returning to the patient.
The dialysate and replacement liquids are both generally made from purified water into which various additive solutions and/or powders are mixed to create respective liquid solutions that are usually substantially isotonic to blood. Often this mixing of additives with purified water may be effected at and/or by each discrete dialysis machine (also known as a monitor) during each dialysis session. This process is often referred to as on-line dialysate or replacement liquid preparation. A centralized, substantially continuous supply of purified water may then preferably be presented to one or more of such on-line dialysis machines in a particular setting such as a hospital or a dialysis clinic for the preparation of these respective liquids during operation.
In a centralized water supply system such as this, it is common to provide a centralized purification arrangement including a reverse osmosis (R/O) apparatus or unit and/or a de-ionization (DI) apparatus or unit among other purification devices, such as carbon and/or mechanical filters and/or chemical treatment devices such as water softeners. There may also be additional water treatment for the removal of bacteria and/or endotoxins or the addition of or subjection to electromagnetic waves, e.g., ultraviolet light for the inactivation or destruction of such pathogens. In any event, the R/O or DI unit commonly establishes the last purification step in the purification arrangement which, as is known in the art, then provides output purified water to medically acceptable and/or otherwise preferable or desirable quality or like standards.
As mentioned above, this purified water may then be delivered in a typical dialysis setting to one or a plurality of dialysis machines, preferably through short branch connections emanating from a main or central supply line. The central supply line may then provide for the flow any unused water to a drain or it may form a circuit by feeding back into one or more of the purification devices (such as the R/O unit) for re-purification and/or to other units (such as a central storage tank) and then/thereby provide for recirculation out to and through the central supply line circuit.
Other machines that use purified water have also been known to be commonly connected to such a centralized water supply line. An example particularly fitting within a hospital or dialysis clinic setting is the connection to the purified water circuit of one or more dialyzer re-use machines (also known as dialyzer reprocessing machines). As is understood, dialyzer re-use machines use the purified water to clean dialyzers after respective dialysis sessions for re-use in later dialysis procedures.
One common concern arising from such an incorporation of dialyzer re-use machines is the relatively high water demand such re-use machines usually require to complete their cleaning procedures. Re-use machines normally require a high volume (though usually intermittent) flow rate of water, albeit usually for a short time period when compared with the lower (usually more constant) demand, longer-term dialysis machine use. However, contemporary centralized purified water circuits often have relatively constant maximum output flow rates, depending ordinarily upon the maximum output of the respective R/O unit if, as is common, the R/O unit feeds directly into the main water supply circuit. The high demands of one or more re-use machines connected to a main supply line can then significantly negatively impact a centralized water supply system having an R/O unit which directly feeds water at a constant maximum output. The negative impact of the high demand is such that it may overburden the main water supply system by drawing too much water flow from the main supply line to the point that the flow of purified water provided simultaneously to any other water using machines such as one or more dialysis machines may be reduced, interrupted or the central line pressure may be decreased sufficiently so that one or more of the dialysis machines do not have sufficient water volume or pressure to continue producing dialysate and/or replacement fluid, as needed for the dialysis procedure, and may thus be forced into an alarm state and possible automatic shut-down. Such alarms and possible shut downs may then provide a danger to the dialysis patient(s).
Note, R/O and/or DI feeding into intervening holding tanks is known in the art. However, such tanks have been disposed in the primary water circuit, and as such are often necessarily unacceptably too large (approximately 250 gallons) for many medical/dialysis settings and/or have too many stagnation areas (as in bladder surge tanks) thus providing unacceptable opportunities for undesirable biological and/or microbiological growth. Additionally, these prior holding tank systems must maintain high flow rates throughout their piping systems to maintain turbulent flow, which minimizes bacterial growth. There are usually large pressure drops through such piping systems due to the high flow rates and long lengths of the piping system as well as due to the number of taps for each water using unit to be attached to the piping system. Intermittent high demand devices such as dialyzer re-use equipment draw large amounts of water out of the piping system in a short period of time. This may cause the pressure levels to drop sharply throughout the piping system, thereby likely causing both the re-use equipment and any other attached water-using equipment, such as dialysis machines, to not have sufficient water volume and/or pressure to operate properly.
Other industrial water usage machines and water supply circuits may also suffer similar drawbacks. Such systems may include pharmaceutical preparation processes and/or electronic device (e.g., microchip) manufacturing processes. Thus, any system that may include the use of both low and high water demand devices on a water supply line may take advantage of the present invention.
Hence, a need exists for providing for a safe, non-overburdensome connection of high water demand devices, like dialyzer re-use machines, to a water supply line so that other lower demand machines, such as dialysis machines, may be provided with a sufficient, uninterrupted supply of water volume, pressure and/or flow rates to maintain normal operations. It is toward this and related aims that the present invention is directed.